Coiled Tubing Injector Skate

ABSTRACT

A coiled tubing injector skate having rollers that independently adjust position to more uniformly distribute roller loading forces is provided. The skate includes a frame and at least one roller having a roller shaft with a first end retained by the frame and a second end retained by the frame. A first resiliently compressible material is disposed between the first end of the roller shaft and the frame. A second resiliently compressible material disposed between the second end of the roller shaft and the frame.

FIELD OF THE INVENTION

The present invention relates generally to coiled tubing injectors, and more particularly, relating to coiled tubing injector skates.

BACKGROUND OF THE INVENTION

Coiled tubing also referred to as coiled pipe or continuous pipe is conventionally used in the oil and gas industry. The coiled tubing is stored on a reel, and during use the tubing is unwound from the reel and inserted into a well. The coiled tubing is inserted and removed from a well using a device commonly referred to as a coiled tubing injector.

Coiled tubing injectors are well known in the technological field of the invention, and conventionally include a pair of continuous chain loops to which are attached a plurality of tubing gripper blocks. As the chain loops are driven, confronting tubing gripper blocks are pressed together on opposite sides of the coiled tubing and grip the exterior of the coiled tubing. The coiled tubing, grasped by the tubing gripper blocks, is conveyed in the same direction as the tubing gripping blocks. Examples of coiled tubing injectors are shown in U.S. Pat. Nos. 6,892,810; 6,216,780; 5,918,671; 5,553,668 and 5,188,174, which are incorporated herein in their entirety by reference.

The tubing gripper blocks are pressed together by skates that are positioned on opposite sides of the coiled tubing with the tubing gripper blocks running between the tubing and the skates. The skates include rollers which engage the tubing gripper blocks and provide a rolling contact surface between the moving gripper blocks and the skates. Hydraulic cylinders or other mechanisms are used to force the oppositely positioned skates together which cause the tubing gripper blocks to press against the tubing. A significantly high force is applied to the skates to cause the tubing gripper blocks to grip the coiled tubing with a sufficiently great force that prevents the tubing from slipping between the tubing gripper blocks.

The skate rollers bear the force exerted upon the tubing gripping blocks, and thus during use are under a considerably high loading force. Consequently, the rollers have a limited cycle life. Further, the cycle life of the rollers is reduced as a result of non-uniform loading across the rollers as a result of inconsistent manufacturing tolerances within the rollers themselves and inconsistent manufacturing tolerances within the various other elements forming the coiled tubing injector. Additionally, during use the gripper blocks and/or chain loops may become misaligned also creating a non-uniform loading on the rollers. Replacement of the rollers is an expensive and time consuming task, and thus it is desirable to minimize the frequency of replacement. Accordingly, there is a need and a desire for a device and/or system that reduces wear and fatigue on the rollers due to non-uniform loading.

SUMMARY OF THE INVENTION

Embodiments of the present invention addresses this need by providing a coiled tubing injector skate having a roller mounting arrangement that permits each roller to independently adjust its position to more uniformly distribute loading across the roller.

Embodiments of the present invention also provide a coiled tubing injector skate having rollers that are each independently mounted to the skate by separate resilient floating mounts.

To achieve these and other advantages, in general, in one aspect, a coiled tubing injector skate is provided. The skate includes a frame and at least one roller having a roller shaft with a first end retained by the frame and a second end retained by the frame. A first resiliently compressible material is disposed between the first end of the roller shaft and the frame. A second resiliently compressible material disposed between the second end of the roller shaft and the frame.

In general, in another aspect, the skate further includes a force distributing disc disposed between the first end of the roller shaft and the first resiliently compressible material, and a force distributing disc disposed between the second end of the roller shaft and the second resiliently compressible material.

There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood and in order that the present contribution to the art may be better appreciated.

Numerous objects, features and advantages of the present invention will be readily apparent to those of ordinary skill in the art upon a reading of the following detailed description of presently preferred, but nonetheless illustrative, embodiments of the present invention when taken in conjunction with the accompanying drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of descriptions and should not be regarded as limiting.

As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.

For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings illustrate by way of example and are included to provide further understanding of the invention for the purpose of illustrative discussion of the embodiments of the invention. No attempt is made to show structural details of the embodiments in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. Identical reference numerals do not necessarily indicate an identical structure. Rather, the same reference numeral may be used to indicate a similar feature of a feature with similar functionality. In the drawings:

FIG. 1 is a diagrammatic perspective view of a pair of opposing coiled tubing injector skates constructed in accordance with the principles of an embodiment of the invention acting upon confronting tubing gripper blocks and a section of tubing;

FIG. 2 is a back perspective view of a coiled tubing injector skate constructed in accordance with the principles of an embodiment of the present invention;

FIG. 3 is a front perspective view of a coiled tubing injector skate constructed in accordance with the principles of an embodiment of the present invention;

FIG. 4 is an enlarged, partial and exploded perspective view a coiled tubing injector skate constructed in accordance with the principles of an embodiment of the present invention;

FIG. 5 is an exploded perspective view of a roller constructed in accordance with the principles of an embodiment of the present invention;

FIG. 6 is a side elevation view of a coiled tubing injector skate constructed in accordance with the principles of an embodiment of the present invention;

FIG. 7 is a cross-sectional view through a mounted roller and the skate taken along line 7-7 in FIG. 6;

FIG. 8 is an enlarged detail view as indicated in FIG. 7;

FIG. 9 is a loading diagram of a mounted roller;

FIG. 10 is a loading diagram of a resilient compression material utilized in the floating mount of a roller; and

FIG. 11 is a loading graph of a resultant roller load as a function the compression of the resilient compression material and the applied load.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1 there is representatively illustrated a pair of oppositely mounted skates 10 a, 10 b, each of which are constructed in accordance with the principles of an embodiment of the present invention, and are for use in connection with a coiled tubing injector. Skates 10 a, 10 b are pushed together by hydraulic cylinders (not shown) to press together a series of confronting pairs of tubing gripper blocks 12 a, 12 b against tubing 14 that is disposed between the skates 10 a, 10 b. The force exerted by the hydraulic cylinders upon each skate 10 a, 10 b is generally represented by force vectors F. Conventionally, each pair of gripper blocks 12 a, 12 b are connected to driven chains, not shown for the purpose of illustrative clarity, to convey the gripper blocks across the skates 10 a, 10 b while being pressed together, and thus convey the tubing 14 between the skates.

Skates 10 a, 10 b are identical, and thus a discussion of only skate 10 a is required.

With reference to FIGS. 2, 3, and 4, skate 10 a includes an elongated beam or frame 18 and a plurality of rollers 20 mounted to the frame along the inward facing side 30. Rollers 20 provide a rolling bearing surface against which gripper blocks 12 a are pressed and conveyed when gripping tubing 14 (not shown), for purpose of illustrative clarity only a single gripper block is illustrated. As will be described in further detail below, rollers 20 are mounted to frame 18 in a fashion that permits each roller to independently float or move with respect to the frame. The ability for each roller 20 to independently float permits the positioning of each roller to separately adjust to irregular geometries of the roller itself, frame 18, gripper blocks 12 a, tubing 14 and/or other elements that otherwise create uneven pressure distribution across the rollers 20 resulting in increased wear and fatigue. The floating mount of each roller 20 reduces wear and fatigue caused by irregular geometries, and thus increases the service life of the roller.

With continued reference to FIGS. 2, 3, and 4, frame 18 includes a back side 28, a front side 30 and a longitudinally extending channel 22 defined by forwardly projecting, longitudinal flanges 24, 26 that extend from the front side of the frame. Each roller 20 includes a roller axel or shaft 32 to which it is rotatably mounted. Each roller 20 is disposed within channel 22 with the roller extending transversely with respect to the frame 18 between flanges 24, 26. Opposite ends 34, 36 of the shaft 32 are received by cooperatively aligned slots 38, 40 extending through flanges 24, 26, respectively. The end 34 of each shaft 32 is retained in its respective slot 38 by a cap plate 42 that is mounted to a forward facing edge 44 of flange 24 by a plurality of threaded fasteners 46 extending cooperating holes 48, 50. Similarly, the end 36 of each shaft 32 is retained in its respective slot 40 by cap plate 52 that is mounted to the forward facing edge 54 of flange 36 by a plurality of threaded fasteners 46 extending cooperating holes 56, 58. Cap plates 42, 52 extend the length of flanges 24, 26, respectively, and cover or close slots 38, 40, thereby preventing withdrawal of the shaft ends 34, 36 from the slots.

With further reference to FIG. 5, there is illustrated an exploded assembly of roller 20, shaft 32 and wear washers 60, 62. A longitudinal length of each shaft end 34, 36 is squared off for reception by the slots 38, 40 and to provide a flat bearing surface for a dampening system that will be further described below. Additionally, the squared off ends 34, 36 prevent shaft 32 from rotating about its own axis once received by slots 38, 40. In an embodiment, roller 20 may be a needle roller bearing. Additionally, shaft 32 may include a grease passage 64 for lubricating the roller 20 upon shaft 32.

With reference to FIG. 4 and FIGS. 6 through 8, a bottom face 66, 68 of slots 38, 40 include a blind-hole 70, 72. A cylindrical-shaped elastomeric element 74, 76 is inserted into the blind-hole 70, 72 followed by a force distributing disc 78, 80. Disc 78, 80 include an alignment boss 86, 88 that extends from one side thereof and which is received by elastomeric element 74, 76 for the purpose of aligning the disc with the elastomeric element. It is important to note that elastomeric elements 74, 76 each represent different possible embodiments thereof, and while elastomeric element 74 is illustrated being received by hole 70 and elastomeric element 76 is illustrated being received by hole 72, in application either or may be utilized in either or both holes. That is, the invention is not limited in any manner by the illustration of hole 70 receiving elastomeric element 74 and hole 72 receiving elastomeric element 76.

Further, while elastomeric elements 74, 76 each represent different structural features, they share the common principle function of providing a biasing force. Accordingly, the following discussion will address the principal function, and then the specific features of each elastomeric element.

Now beginning with the principle function, elastomeric element 74, 76 and disc 78, 80 are appropriately sized such that the disc protrudes from the blind-hole 70, 72 a distance dLo. In this manner, a flat side 82, 84 of shaft ends 34, 36 bears against the disc 78, 80 and is spaced from bottom face 66, 68 a distance equal to dLo. Accordingly, shaft ends 34, 36 are capable of limited vertical movement within slots 38, 40 and with respect to frame 18 against the spring force of the elastomeric element 74, 76. Additionally, this mounting configuration permits the roller shaft 32 to rock about an axis perpendicular to the roller shaft. The spring force exerted by the elastomeric element 74, 76 upon compression may be adjusted as desired through the selection of a material having a desired or suitable elastic modulus. FIGS. 9, 10, and 11 are force diagrams illustrating the force distribution across the roller and elastomeric elements, and the relational dimensional characteristics thereof.

In a first embodiment, elastomeric element 74 includes a spherically-shaped recess 90 formed through one end 92 thereof that is configured to receive boss 86 therein to axially align disc 78 therewith. Additionally, to permit desired compression of the elastomeric element 74, is of a diameter that provides a radial gap r between the side of the elastomeric element and the sidewall of blind-hole 70.

In a second embodiment, elastomeric element 76 includes an axial through-passage 94 into which is received boss 88 of disc 80 to axially align the disc and elastomeric element. In this embodiment, the elastomeric element 76 is configured to have a diameter such that there is no radial gap between the side thereof and the sidewall of blind-hole 72, and the through-passage 94 permits a desired compression of the elastomeric element. Again, it is important to understand, that discs, 78, 80, elastomeric elements 74, 76 and blind-holes 70, 72 may be utilized interchangeable, and the invention is not limited to the illustrated configuration.

A number of embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims. 

What is claimed is:
 1. A coiled tubing injector skate comprising: a frame; at least one roller having a roller shaft with a first end retained by said frame and a second end retained by said frame; a first resiliently compressible material disposed between said first end of said roller shaft and said frame; and a second resiliently compressible material disposed between said second end of said roller shaft and said frame.
 2. The coiled tubing injector skate of claim 1, further comprising: a first force distributing disc disposed between said first end of said roller shaft and said first resiliently compressible material; and a second force distributing disc disposed between said second end of said roller shaft and said second resiliently compressible material.
 3. The coiled tubing injector skate of claim 2, wherein said first and said second resiliently compressible material is cylindrically shaped.
 4. The coiled tubing injector skate of claim 3, wherein either of said first and said second resiliently compressible material includes a spherical recess on an end thereof or an axial through-passage.
 5. The coiled tubing injector skate of claim 1, wherein said frame includes first and second flanges projecting from an inward side thereof between which said at least one roller extends, said first flange retaining said first end of said roller shaft and said second flange retaining said second end of said roller shaft.
 6. The coiled tubing injector skate of claim 5, further comprising: a first force distributing disc disposed between said first end of said roller shaft and said first resiliently compressible material; and a second force distributing disc disposed between said second end of said roller shaft and said second resiliently compressible material.
 7. The coiled tubing injector skate of claim 6, wherein said first force distributing disc and said first resiliently compressible material are received by said frame; and wherein said second force distributing disc and said second resiliently compressible material are received by said frame.
 8. A coiled tubing injector skate comprising: an elongate frame having first and second flanges extending from a forward side of said elongated frame and defining an elongated channel therebetween; a first plurality of rollers, each roller of said first plurality of rollers extending between said first and said second flanges, and having a roller shaft with a first end retained by said first flange and a second end retained by said second flange; and a dampening element of a compressible material disposed between each of said first roller shaft ends and each of said second roller shaft ends of said first plurality of rollers.
 9. The coiled tubing injector skate of claim 8, further comprising a force distribution disc disposed between each dampening element and roller shaft end.
 10. The coiled tubing injector skate of claim 9, wherein each of said dampening elements is cylindrical shaped.
 11. The coiled tubing injector skate of claim 10, wherein each of said dampening elements and force distribution discs are received within a blind-hole. 